Mcrypt ciphers

Here is a list of ciphers which are currently supported by the mcrypt
extension. For a complete list of supported ciphers, see the defines at
the end of mcrypt.h. The general rule with the
mcrypt-2.2.x API is that you can access the cipher from PHP with
MCRYPT_ciphername. With the libmcrypt-2.4.x and libmcrypt-2.5.x API these constants also work,
but it is possible to specify the name of the cipher as a string with a
call to mcrypt_module_open().

MCRYPT_3DES

MCRYPT_ARCFOUR_IV (libmcrypt > 2.4.x only)

MCRYPT_ARCFOUR (libmcrypt > 2.4.x only)

MCRYPT_BLOWFISH

MCRYPT_CAST_128

MCRYPT_CAST_256

MCRYPT_CRYPT

MCRYPT_DES

MCRYPT_DES_COMPAT (libmcrypt 2.2.x only)

MCRYPT_ENIGMA (libmcrypt > 2.4.x only, alias for MCRYPT_CRYPT)

MCRYPT_GOST

MCRYPT_IDEA (non-free)

MCRYPT_LOKI97 (libmcrypt > 2.4.x only)

MCRYPT_MARS (libmcrypt > 2.4.x only, non-free)

MCRYPT_PANAMA (libmcrypt > 2.4.x only)

MCRYPT_RIJNDAEL_128 (libmcrypt > 2.4.x only)

MCRYPT_RIJNDAEL_192 (libmcrypt > 2.4.x only)

MCRYPT_RIJNDAEL_256 (libmcrypt > 2.4.x only)

MCRYPT_RC2

MCRYPT_RC4 (libmcrypt 2.2.x only)

MCRYPT_RC6 (libmcrypt > 2.4.x only)

MCRYPT_RC6_128 (libmcrypt 2.2.x only)

MCRYPT_RC6_192 (libmcrypt 2.2.x only)

MCRYPT_RC6_256 (libmcrypt 2.2.x only)

MCRYPT_SAFER64

MCRYPT_SAFER128

MCRYPT_SAFERPLUS (libmcrypt > 2.4.x only)

MCRYPT_SERPENT(libmcrypt > 2.4.x only)

MCRYPT_SERPENT_128 (libmcrypt 2.2.x only)

MCRYPT_SERPENT_192 (libmcrypt 2.2.x only)

MCRYPT_SERPENT_256 (libmcrypt 2.2.x only)

MCRYPT_SKIPJACK (libmcrypt > 2.4.x only)

MCRYPT_TEAN (libmcrypt 2.2.x only)

MCRYPT_THREEWAY

MCRYPT_TRIPLEDES (libmcrypt > 2.4.x only)

MCRYPT_TWOFISH (for older mcrypt 2.x versions, or mcrypt > 2.4.x )

MCRYPT_TWOFISH128 (TWOFISHxxx are available in newer 2.x versions, but not in the 2.4.x versions)

MCRYPT_TWOFISH192

MCRYPT_TWOFISH256

MCRYPT_WAKE (libmcrypt > 2.4.x only)

MCRYPT_XTEA (libmcrypt > 2.4.x only)

You must (in CFB and OFB mode)
or can (in CBC mode) supply an
initialization vector (IV) to the respective cipher function. The
IV must be unique and must be the same when
decrypting/encrypting. With data which is stored encrypted, you
can take the output of a function of the index under which the
data is stored (e.g. the MD5 key of the filename).
Alternatively, you can transmit the IV together with the encrypted
data (see chapter 9.3 of Applied Cryptography by Schneier (ISBN 0-471-11709-9) for a
discussion of this topic).